1. Field of the Invention
The present invention relates generally to communications systems. More particularly, the invention relates to decoding of encoded data in a communications system.
2. Description of the Related Art
Currently many conventional communications systems use forward error correction (FEC) coding to improve bit error rates at low received energy levels. Ideally, in communications links, received signal strength is often comparable to that of noise. Additionally, due to bandwidth concerns, bandwidth efficient modulation (BEM) schemes with high spectral efficiency are currently used in the new standards such as ATSC and DVB-H. These standards use high code rate Reed Solomon (RS) codes.
High spectral efficiency links commonly use either a rate 0.875 or 0.9 RS code with a block length of 255 symbols. Long block length FEC codes such as RS codes can be used for data and video transfers. Additionally, long block length FEC codes are used in scenarios where the error floor obtained using turbo codes is undesirable. Previous researchers have developed soft decision (SD) RS decoding algorithms, often referred to as Guruswami-Sudan (GS) SD decoding or GS SD RS decoding. However, the GS SD RS decoding algorithm is computationally complex because the algorithm requires estimating polynomials in the Galois field and then factoring these polynomials to estimate a list of possible valid codewords. The computational complexity of the GS SD RS decoding algorithm is proportional to n2m4 where n is the block length of the RS code and m is the required multiplicity of the polynomial.